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Press Release: Study Explores Groundwater and Geothermal Energy in Drought-Stricken Eastern Oregon and Neighboring States

Technical Announcement: USGS Issues Revised Framework for Hydrogeology of Floridan Aquifer

Press Release: High Plains Aquifer Groundwater Levels Continue to Decline

Regional Groundwater Availability Study Geospatial Data

Press Release: USGS Assesses Current Groundwater-Quality Conditions in the Williston Basin Oil Production Area

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USGS Groundwater Watch

USGS maintains a network of active wells to provide basic statistics about groundwater levels.

Other Water Topics

 Water Resources

 Groundwater

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USGS Water Science Centers are located in each state.

Water-Table Fluctuation (WTF) Method

The water-table fluctuation (WTF) method provides an estimate of groundwater recharge by analysis of water-level fluctuations in observation wells. The method is based on the assumption that a rise in water-table elevation measured in shallow wells is caused by the addition of recharge across the water table.

Determination of water-level rise.

Recharge by the WTF method is estimated as:

R(t_j) = Sy* DH(t_j)       (1)

where R(t_j) (cm) is recharge occurring between times t₀ and t_j, Sy is specific yield (dimensionless), and DH(t_j) is the peak water level rise attributed to the recharge period (cm).

Although simple in theory, some key assumptions and critical issues inherent in the WTF method have great bearing on its successful application: (1) the observed well hydrograph depicts only natural water-table fluctuations caused by groundwater recharge and discharge; (2) Sy is known and constant over the time period of the water-table fluctuations, and (3) the pre-recharge water-level recession can be extrapolated to determine DH(t_j).

Application of the method WTM involves two steps:

• Estimating the water-level rise DH(t_j)
• Estimating specific yield Sy

Because of the simplicity of the method and wide availability of water-level hydrographs from observation wells, the WTF method has been used for many years (Meinzer, 1923; Rasmussen and Andreasen, 1959; Crosbie and others, 2005). An excellent review of the WTF method is provided in Healy and Cook (2002).

Case Studies Using the WTF Method

References